title: Effects of L-type Ca2+ channel blocker nifedipine on dynamic arterial blood pressure control.
abstract: Dynamic characteristics of arterial pressure (AP) regulation are important components in our understanding of rapid AP restoration by the arterial baroreflex system. The present study examined the effects of an L-type Ca(2+) channel blocker nifedipine on baroreflex-mediated dynamic AP regulation. In anesthetized and vagotomized rats, carotid sinus pressure was externally perturbed using a Gaussian white noise signal, and the neural arc transfer function from pressure input to efferent sympathetic nerve activity (SNA) and the peripheral arc transfer function from SNA to AP were identified. The peripheral arc transfer function approximated a second-order low-pass filter with pure dead time. Intravenous administration of nifedipine significantly decreased the steady-state gain and increased the damping ratio of the peripheral arc without affecting the dynamic characteristics of the neural arc. When the step response of AP was calculated based on the peripheral arc transfer function alone, nifedipine prolonged 80% rise time by 26%. When the closed-loop AP response was simulated based on both the neural arc and peripheral arc transfer functions and the dynamic gain of the baroreflex total loop was assumed to be 2.0, nifedipine prolonged 80% recovery time by 107%. In conclusion, L-type Ca(2+) channel blockade may compromise the baroreflex-mediated AP control not only in the magnitude but also in the speed of AP restoration.
authors.forename: Toru
authors.initials: T
authors.lastname: Kawada
authors.forename: Hiromi
authors.initials: H
authors.lastname: Yamamoto
authors.forename: Shuji
authors.initials: S
authors.lastname: Shimizu
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Turner
authors.forename: Masaru
authors.initials: M
authors.lastname: Sugimachi
mesh_terms: D000818:Animals; D062186:Arterial Pressure / Q000187:drug effects*; D017704:Baroreflex / Q000187:drug effects; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D020746:Calcium Channels, L-Type / Q000378:metabolism; D002346:Carotid Sinus / Q000187:drug effects / Q000502:physiology; D004353:Drug Evaluation, Preclinical; D009543:Nifedipine / Q000494:pharmacology*; D051381:Rats; D011921:Rats, Inbred WKY
chemical_list: D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D009543:Nifedipine